System and method for fuel nozzle cleaning during engine operation

ABSTRACT

A method and system for cleaning a fuel nozzle during engine operation is provided. Operations include operating the compressor section to provide the flow of oxidizer at a first oxidizer flow condition to the combustion chamber, wherein the first oxidizer flow condition comprises an environmental parameter; operating the fuel system at a first fuel flow condition to produce a fuel-oxidizer ratio at the combustion chamber; comparing the environmental parameter to a first environmental parameter threshold; and transitioning the fuel system to a second fuel flow condition corresponding to a cleaning condition at the fuel nozzle if the environmental parameter is equal to or greater than the first environmental threshold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/809,797 filed on Mar. 5, 2020, the contents of which are herebyincorporated by reference in their entirety.

FIELD

The present subject matter relates generally to methods and systems forfuel nozzle cleaning during operation of a heat engine. Particularaspects of the present subject matter relate to methods and systems forfuel nozzle cleaning during operation of a gas turbine engine. Stillparticular aspects of the present subject matter relate to fuel nozzlecleaning during in-flight operation of a propulsion system.

BACKGROUND

Heat engines, such as gas turbine engines, experience fuel coking withina fuel nozzle when fuel inside the fuel nozzle is exposed to hightemperatures during engine operation. Fuel coking may particularly occurduring low fuel-flow conditions and with exposure to high temperaturesduring operation. Fuel coking in the fuel nozzle may also occurfollowing engine shutdown, such as due to thermal soaking of the fuelnozzle and residual fuel within the fuel nozzle following shutdown.

Fuel coke build-up may adversely affect fuel nozzle performance, andoverall engine performance, durability, or operability, such as byundesirably restricting or clogging fuel flow through the fuel nozzle.Such restricted fuel flow may generally result in uneven spray patterns,which may accelerate deterioration of components at the combustionsection and/or turbine section. Component deterioration may result fromincreased circumferential or radial thermal gradients, or hot spots, ordamage caused by increased combustion dynamics, such as pressureoscillations, acoustics, or other uneven wear and damage. Suchrestricted fuel flow may also cause pressure build-up at a fuel system,such as to reach fuel system pressure limits, which may cause loss ofengine thrust control.

As such, there is a need for improved cleaning system and methods thataddress these issues.

BRIEF DESCRIPTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

An aspect of the present disclosure is directed to a heat engineincluding a compressor section configured to provide a flow of oxidizerto a combustion chamber; a fuel nozzle including a plurality of fuelinjection openings, wherein the fuel nozzle is configured to provide afirst fuel flow to the combustion chamber through one or more of thefuel injector openings and a second fuel flow to the combustion chamberthrough one or more of the fuel injector openings different from thefirst fuel flow; a fuel system including a first conduit configured toprovide the first fuel flow to the combustion chamber and a secondconduit configured to provide the second fuel flow to the combustionchamber, wherein the fuel system is configured to provide the first fuelflow variably and separate from the second fuel flow; and a controllerconfigured to execute operations, the operations including operating thecompressor section to provide the flow of oxidizer at a first oxidizerflow condition to the combustion chamber, wherein the first oxidizerflow condition comprises an environmental parameter; operating the fuelsystem at a first fuel flow condition to produce a fuel-oxidizer ratioat the combustion chamber; comparing the environmental parameter to afirst environmental parameter threshold; and transitioning the fuelsystem to a second fuel flow condition corresponding to a cleaningcondition at the fuel nozzle if the environmental parameter is equal toor greater than the first environmental threshold.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a perspective view of an embodiment of an aircraft accordingto an aspect of the present disclosure;

FIG. 2 is a schematic cross-sectional view of an embodiment of a heatengine including a controller configured to execute steps of a methodaccording to aspects of the present disclosure;

FIG. 3 is a schematic view of an exemplary combustion and fuel systemaccording to an aspect of the present disclosure;

FIG. 4 is an exemplary graph depicting a cleaning condition at whichsteps of the method of FIGS. 5A-5B may be performed;

FIGS. 5A-5B are a flowchart outlining steps of a method for fuel nozzlecleaning during engine operation according to aspects of the presentdisclosure; and

FIG. 6 is an exemplary graph depicting portions of the method for fuelnozzle cleaning during engine operation according to aspects of thepresent disclosure.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

As used herein, the terms “first”, “second”, and “third” may be usedinterchangeably to distinguish one component from another and are notintended to signify location or importance of the individual components.

The terms “upstream” and “downstream” refer to the relative directionwith respect to fluid flow in a fluid pathway. For example, “upstream”refers to the direction from which the fluid flows, and “downstream”refers to the direction to which the fluid flows.

Embodiments of a method and system for cleaning a fuel nozzle duringengine operation are provided herein. Embodiments of the method andsystem provide control and execution of conditions allowing for removalof fuel deposits, such as fuel coke, from within a fuel nozzle duringoperation of an engine. The fuel deposits may be broken-down intolighter and/or smaller particles via thermal decomposition, allowing fortheir egress from the fuel nozzle. In various embodiments, the fueldeposits may be forcibly or abrasively removed via a cleaning fluidand/or fluid purge. In certain embodiments, the methods and systemsprovided herein allow for fuel nozzle cleaning during in-flightoperation of the engine as an aircraft propulsion system. Embodiments ofthe methods and systems depicted and described herein may include stepsfor operating a fuel system to thermally decompose deposits at the fuelnozzle and determining conditions for executing cleaning steps.Embodiments of the methods and systems provided herein may improve life,durability, maintenance, and/or performance of other combustion sectionand/or turbine section components, such as by reducing or eliminatinguneven fuel nozzle spray patterns, reducing circumferential and/orradial thermal gradient variations (e.g., reducing hot spots), orreducing other conditions that may cause uneven or increased wear ordeterioration of certain combustion section or turbine sectioncomponents.

Referring now to the drawings, in FIG. 1, an exemplary embodiment of anaircraft 100 including a propulsion system 10, a fuel nozzle 60, a fuelsystem 90, and a controller 210 according to an aspect of the presentdisclosure is provided. The aircraft 100 includes an aircraft structureor airframe 105. The airframe 105 includes a fuselage 110 to which wings120 and an empennage 130 are attached. The propulsion system 10according to aspects of the present disclosure is attached to one ormore portions of the airframe. In various embodiments, the propulsionsystem 10 may be configured generally as any appropriate propulsion orpower generation system including a fuel nozzle and fuel systemconfigured to provide fuel to a combustion or detonation chamberaccording to aspects of the disclosure provided herein. In certainembodiments, the propulsion system 10 is configured as a turbofan,turboprop, turbojet, or turboshaft engine, or ramjet or supersoniccombustion ramjet engine, or hybrid-electric engine, or combinationsthereof. In certain instances, the propulsion system 10 is attached toan aft portion of the fuselage 110. In certain other instances, thepropulsion system 10 is attached underneath, above, or through the wing120 and/or portion of the empennage 130.

As described in further detail herein, the aircraft 100 including thepropulsion system 10 is configured to execute operations or manoeuvresduring ground operation, takeoff, and in-flight. The aircraft and engineoperations or manoeuvres may include those associated with alanding-takeoff (LTO) cycle. The LTO cycle includes idle, takeoff,climb, and approach. The LTO cycle may generally include certain thrustoutput settings from the engine 15. However, in various embodiments,aircraft 100 and propulsion system 10 operations or manoeuvres mayinclude other or additional steps providing for changes in engine thrustoutput or power generation, altitude or attitude, or combinationsthereof, resulting in changes to ambient and inlet parameters at thepropulsion system 10 or aircraft 100. Portions of the LTO cycle mayfurther be associated with certain emissions or noise limits, such as,but not limited to, limits to emissions of oxides of nitrogen (NO_(x)),carbon monoxide (CO), carbon dioxide (CO₂), unburned hydrocarbons (UHC),or smoke, or perceived acoustic noise, from the propulsion system 10.

Referring now to FIG. 2, an embodiment of a heat engine 15 is provided.The propulsion system 10 of FIG. 1 may include the engine 15 provided inFIG. 2. In various embodiments, the engine 15 may be configured as apropulsion system, a power generation system, a hybrid electric engine,or other heat engine apparatus including a fuel system 90 configured toprovide liquid and/or gaseous fuel to a fuel nozzle 60 according toaspects of the present disclosure. The engine 15 may generally beconfigured as a turbo machine, such as a gas turbine engine including acompressor section 42, a combustion section 44, and a turbine section 46in serial flow arrangement. Certain embodiments of the engine 15 areconfigured as a turbofan or turbojet engine including a fan assembly 14operatively connected to a core engine 40. Still various embodiments maydefine the engine 15 as an open rotor, propfan, or Brayton cyclemachine. Still further, certain embodiments may include a power gearassembly operably coupled to the fan assembly 14 and at least a portionof the turbine section 46. The core engine 40 is positioned in serialflow arrangement with the fan assembly 14.

The engine 15 includes an inlet 18 through which a flow of oxidizer,depicted schematically by arrows 22, enters the engine 15. Inparticular, the flow of oxidizer 22 enters the core engine 40. The flowof oxidizer 22 is compressed by the compressor section 42 beforeentering the downstream combustion section 44. The combustion section 44includes a fuel nozzle 60 according to embodiments described herein inregard to FIG. 3. A fuel system 90 provides a first fuel flow and asecond fuel flow to the fuel nozzle 60. During certain operations of theengine 15 according to aspects of the disclosure provided herein, thefirst fuel flow and/or second fuel flow is mixed with the flow ofoxidizer 22 and burned or detonated to produce combustion gases. Thecombustion gases release energy to drive the turbine section 46, whichdrives the compressor section 42.

Referring now to FIG. 3, an exemplary embodiment of a combustion section44 including a fuel nozzle 60 and the fuel system 90 according to anaspect of the present disclosure is provided. The combustion section 44may be configured as any suitable type of combustor, such as, but notlimited to, a deflagrative combustor, a detonation combustor (e.g.,pulse detonation, rotating detonation, etc.), a trapped vortexcombustor, can-type combustor, can-annular type combustor, annularcombustor, volute combustor, or combinations thereof. The combustionsection 44 includes a detonation or combustion chamber 72 at which aliquid and/or gaseous fuel is burned with oxidizer 22, such as describedherein. The fuel nozzle 60 is configured as any appropriate type of fuelnozzle including a first injector 61 and a second injector 62. The firstinjector 61 is configured to receive a first fuel flow from the fuelsystem 90, depicted schematically by arrows 91. The second injector 62is configured to receive a second fuel flow from the fuel system 90,depicted schematically by arrows 92. The first injector 61 is configuredto provide the first fuel flow 91 to the combustion chamber 72. The fuelnozzle 60 includes a plurality of fuel injection openings through whichrespective flows of fuel are provided from the fuel nozzle 60 to thecombustion chamber 72. The plurality of fuel injection openings includesa first opening 67 corresponding to the first injector 61 and a secondopening 68 corresponding to the second injector 62.

In certain embodiments, the combustion section 44 includes a pluralityof the fuel nozzle 60, e.g., in circumferential arrangement, or otherappropriate arrangement. In still certain embodiments, the fuel nozzle60 is configured as a rich burn, lean burn, or other appropriate typefuel nozzle. In particular embodiments, the fuel nozzle 60 includes oneor more of the first injector 61 and one or more of the second injector62. In certain embodiments, the first injector 61 is configured as amain fuel injector and the second injector 62 is configured as a pilotfuel injector. During nominal operation of the engine 15, fuel system90, and fuel nozzle 60, the main fuel injector may be configured toprovide larger fuel flows to the combustion chamber 72 compared to thepilot fuel injector. For instance, in certain operating conditions ofthe engine (e.g., startup or low power), approximately 100% of the fuelto the combustion chamber 72 may egress through the pilot fuel injector.In other instances, in certain operating conditions of the engine (e.g.,greater than low power, such as mid-power or high-power conditions),most fuel may egress through the main fuel injector. However, duringcertain conditions such as provided herein, fuel flows through therespective injectors 61, 62 will be desirably altered or adjusted awayfrom nominal conditions. It should be appreciated that, in variousembodiments, the first injector 61 may be configured as a pilot fuelinjector and the second injector 62 may be configured as a main fuelinjector.

The fuel system 90 is configured to provide the first fuel flow 91 tothe first injector 61 variably and separate from the second fuel flow 92second injector 62. In certain embodiments, the fuel system 90 includesa first conduit 95 in fluid communication with the first injector 61 ofthe fuel nozzle 60 and a second conduit 96 in fluid communication withthe second injector 62 of the fuel nozzle 60. The fuel system 90 isconfigured to desirably allow and restrict egress of the first fuel flow91 and the second fuel flow 92 to the fuel nozzle 60 separately from oneanother, such as described herein. In one embodiment, the fuel system 90includes a first valve 93 positioned at the first conduit 95 and asecond valve 94 positioned at the second conduit 96, such as to allowfor selective egress and restriction of the respective first fuel flow91 and second fuel flow 92 to the fuel nozzle 60 based on one or moresteps of the method provided herein.

In various embodiments, the combustion section 44 includes a pluralityof combustor components generally defining the combustion chamber 72 orother portions exposed to the hottest portions of the combustion section44. Such combustor components may include a liner assembly 70, a heatshield assembly 74, swirler 76, or the fuel nozzle 60. As furtherdescribed herein, embodiments of the method may include a healthparameter corresponding to a temperature or thermal gradient at one ormore combustor components. In certain embodiments, the health parametercorresponding to the combustor component or turbine section isassociated with limiting an undesired temperature differential orgradient along the individual component or relative to a plurality ofthe component (e.g., a circumferential or radial plurality of thecomponent, such as an annular combustor). The health parameter maycorrespond to desired limits associated with mitigating formation of hotspots at the combustion section 44 or turbine section 46.

In still various embodiments, the health parameter may correspond to alife, durability, or other structural integrity parameter, such asdesired structural life or coating retention period, associated with thecombustor component as a function of combustor stability. In still otherembodiments, the health parameter may correspond to an emissions ornoise parameter at the combustion section 44, such as, but not limitedto, a desired or required emissions output range or perceived noiserange during operation of the engine 15. In certain embodiments, thedesired or required emissions or perceived noise output range is afunction of engine or aircraft operation. For instance, the desired orrequired emissions or perceived noise output range may correspond to anemissions limit corresponding to the LTO cycle, a local emissionsrequirement, or other regulatory requirement.

Referring now to FIG. 4, a graph 500 depicting changes in compressorsection exit conditions corresponding to fuel-oxidizer combustion isprovided. The graph 500 depicts an embodiment of a cleaning envelop atarea 505 at which one or more cleaning methods described herein may beexecuted during operation of an engine, such as the engine 15 (FIG. 2),or such as the propulsion system 10 during operation and/or flight ofthe aircraft 100 (FIG. 1).

The graph 500 includes a first compressor section exit conditionparameter versus a second compressor section exit condition parameter.In various embodiments, the first and second compressor section exitcondition parameters correspond to a location at the engine downstreamof the compressor section and upstream of the combustion chamber. Forinstance, the first and second compressor section exit conditionparameters may generally correspond to the flow of oxidizer to be mixedwith fuel and burned at the combustion chamber. In various instances,the compressor section exit condition parameter may be referred to as aStation 3 parameter at the engine.

In various embodiments, the first compressor section exit conditionparameter includes a compressor section exit pressure. In certainembodiments, the compressor section exit pressure includes a staticpressure parameter. However, in other embodiments, the compressorsection exit pressure parameter is any appropriate pressure parametercorresponding to the flow of oxidizer to be mixed with fuel and burnedat the combustion chamber. In still various embodiments, the secondcompressor section exit condition parameter includes a compressorsection exit temperature of the flow of oxidizer.

Referring now to FIGS. 5A-5B, flowcharts outlining exemplary steps of amethod for fuel nozzle cleaning during engine operation is provided(hereinafter, “method 1000”). Embodiments of the method 1000 providedherein allow for fuel nozzle cleaning while maintaining a desiredcombustion section and/or engine power output or thrust output suitableduring engine operation. Certain embodiments of the method 1000 mayprovide particular benefits, such as fuel nozzle cleaning duringaircraft operation. As described in various embodiments herein, aircraftoperation may include, but is not limited to, conditions generallycorresponding to the LTO cycle. However, other aircraft operation mayinclude flight conditions generally.

Referring now to the flowchart at FIGS. 5A-5B, and in conjunction withthe graph 500, the method 1000 includes at 1010 operating a compressorsection to produce or provide a flow of oxidizer at a first oxidizerflow condition to the combustion chamber. The first oxidizer flowcondition may generally include an environmental parameter correspondingto a range within which the flow of oxidizer allows for cleaning of thefuel nozzle while operating the engine at a desired fuel-oxidizer ratio.In certain embodiments, the environmental parameter includes one or moreof the first compressor section exit temperature parameter, the secondcompressor section exit temperature parameter, the first compressorsection exit pressure parameter, the second compressor section exitpressure parameter, or combination thereof. In various embodiments, thedesired fuel-oxidizer ratio includes any fuel-oxidizer ratio permittingcontinued operation and/or performance of the engine. In certainembodiments, the desired fuel-oxidizer ratio allows continued operationand/or performance of the engine relative to a fuel-oxidizer conditionimmediately preceding fuel nozzle cleaning during engine operation. Instill particular embodiments, the desired fuel-oxidizer ratio includesmaintaining a desired fuel-oxidizer ratio across two or more fuel flowconditions, such as described herein.

Referring to the graph 500 in FIG. 4, the environmental parameter of thefirst oxidizer flow condition at 1010 may generally correspond to atemperature and a pressure of the flow of oxidizer at the combustionsection and from the compressor section. As described above in anembodiment, the environmental parameter corresponds to the first flow ofoxidizer downstream of the compressor section and upstream of thecombustion chamber. For example, the environmental parameter maycorrespond to a Station 3 oxidizer temperature (e.g., T3) and oxidizerpressure (e.g., P3) at the heat engine.

In certain embodiments, the graph 500 in FIG. 4 includes a firstenvironmental parameter threshold, depicted at line 510. In variousembodiments, the first environmental parameter threshold defines a lowerlimit at or above which the cleaning envelop 505 is defined and acleaning method is executed during operation of the engine. In oneembodiment, the first environmental parameter threshold 510 correspondsto the first compressor section exit condition parameter, such asdepicted at line 510A in FIG. 4. In another embodiment, the firstenvironmental parameter threshold 510 corresponds to the secondcompressor section exit condition parameter, such as depicted at line510B in FIG. 4.

In still certain embodiments, the graph 500 includes a secondenvironmental parameter threshold, depicted at line 520 in FIG. 4. Invarious embodiments, the second environmental parameter thresholddefines an upper limit at or below which the cleaning envelop is definedand a cleaning method is executed during operation of the engine. In oneembodiment, the second environmental parameter threshold 520 correspondsto the compressor section exit condition parameter, such as depicted atline 520A in FIG. 4. In another embodiment, the second environmentalparameter threshold 520 corresponds to the second compressor sectionexit condition parameter, such as depicted at line 520B in FIG. 4.

In various embodiments, the environmental parameter thresholdscorrespond to conditions at which the flow of oxidizer allows forthermal decomposition of deposits of fuel within the fuel nozzle. Thefirst oxidizer flow condition may particularly correspond to temperatureand pressure conditions at the fuel nozzle that allow for thermaldecomposition of deposits of fuel or other matter (e.g., carbon buildup,fuel coke, etc. within the first injector and the second injector). Theenvironmental parameter may further correspond to pressure conditions atwhich the fuel nozzle and/or fuel system may allow for purge of fueldeposits, such as fuel coke, from the fuel nozzle into the combustionchamber.

In still certain embodiments, the environmental parameter thresholdscorrespond to conditions at which combustion is sustained orsustainable, such as to provide the flow of oxidizer to the combustionchamber above a first temperature threshold and a first pressurethreshold. The environmental parameter thresholds may furthermorecorrespond to conditions at which desired combustion stability orperformance is maintained, or certain combustion acoustics, pressureoscillations or fluctuations, lean blowout, emissions, or other adverseconditions, are mitigated. In various embodiments, the environmentalparameter thresholds may correspond to one or emissions or noise limitscorresponding to certain portions of the LTO cycle.

It should be appreciated that the environmental parameter includes oneor more particular ranges of temperature and/or pressure of the flow ofoxidizer downstream of the compressor section (e.g., at the fuel nozzle,or at the combustion chamber). Particular ranges of environmentalparameter provided herein may be critical and non-obvious relative toone or more steps of the method 1000 provided herein, such as to allowfor fuel nozzle cleaning during engine operation according to one ormore embodiments provided herein. Various ranges provided herein mayparticularly allow for purge or other removal of fuel coke or debrisfrom the fuel nozzle during operation of the engine. In certainembodiments, the first environmental parameter threshold includes atemperature at or above approximately 550 degrees Fahrenheit(approximately 287 degrees Celsius). In still certain embodiments, thefirst environmental parameter threshold includes a pressure at or aboveapproximately 135 pounds per square inch (psia) (approximately 930kilo-Pascals (kPa)). In other embodiments, the first environmentalparameter threshold is at or above approximately 600 F (approximately315 C). In still other embodiments, the first environmental parameterthreshold is at or above approximately 150 psia (approximately 1030kPa).

In still certain embodiments, the second environmental parameterthreshold includes a temperature at or below approximately 1250 degreesFahrenheit (approximately 680 degrees Celsius). In another embodiment,the second environmental parameter threshold corresponds to a pressureat or below 315 psia (approximately 2172 kPa). In other embodiments, thesecond environmental parameter threshold is at or below approximately1100 F (approximately 595 C). In still other embodiments, the secondenvironmental parameter threshold is at or below approximately 300 psia(approximately 2070 kPa). In still another embodiment, the environmentalparameter corresponds to a pressure range between approximately 175 psiaand approximately 275 psia (between approximately 1205 kPa andapproximately 1900 kPa).

Referring now to FIG. 6, an exemplary graph 400 depicting portions of amethod for fuel nozzle cleaning during engine operation, (hereinafter,“method 1000”) is provided. The graph 400 depicts a plot of a fuelparameter over time. In various embodiments, the fuel parametercorresponds to a fuel flow to a combustion chamber. In certainembodiments, the fuel parameter is fuel flow (e.g., W_(fuel)), or a fuelpressure (e.g., P_(fuel)) corresponding to fuel flow through the fuelsystem and fuel nozzle to the combustion chamber. It should beappreciated that, in various embodiments, any applicable parameter maybe utilized that is indicative of fuel flow to the combustion chamber.

The graph 400 depicts a plurality of fuel flows (e.g., first fuel flowcorresponding to fuel flow rate A, second fuel flow corresponding tofuel flow rate B, etc.) corresponding to a plurality of fuel injectionopenings at a fuel nozzle. The method 1000 may be performed with anengine, controller, fuel system, and fuel nozzle allowing forindependent or separately variable control of fuel flow through two ormore conduits and fuel injection openings at the fuel nozzle.

Generally, the fuel nozzle includes a first injector and a secondinjector, such as described in regard to FIG. 3. The fuel nozzle isconfigured to provide a first fuel flow to the combustion chamberthrough the first injector and a second fuel flow to the combustionchamber through the second injector. The fuel system includes a firstconduit in fluid communication with the first injector at the fuelnozzle, and a second conduit in fluid communication with the secondinjector at the fuel nozzle. The fuel system is configured to providethe first fuel flow through a fuel injection opening of the fuel nozzleto the combustion chamber independent or separately variable from thesecond fuel flow through a second fuel injection opening of the fuelnozzle to the combustion chamber. In certain embodiments, the fuelconduits, the fuel injection openings, or both, correspond to one ormore main fuel injectors separate from one or more pilot fuel injectorsat the fuel nozzle, such as described elsewhere herein.

Referring back to the graph 400, the method 1000 includes a plurality offuel flow conditions according to embodiments of the method providedherein. As further described herein, some or all of the steps of themethod 1000 provided herein may be stored and executed by a controller(e.g., controller 210) or other computing system. Although certain stepsprovided herein may be performed in one or more particular sequentialorders, it should be appreciated that various embodiments of the methodmay re-order, re-sequence, omit, include, or iterate certain steps orcombinations of steps within the scope of this disclosure.

Referring now to FIGS. 4-6, at 1020, the method 1000 includes operatingthe fuel system at a first fuel flow condition, such as depicted at 410on graph 400. The first fuel flow condition 410 includes a first fuelflow rate A, depicted at line 401, corresponding to the first fuel flow91 through the first injector 61 of the fuel nozzle 60 depicted in FIG.3. The first fuel flow condition 410 further includes a first fuel flowrate B, depicted at line 402, corresponding to the second fuel flow 92through the second injector 62 of the fuel nozzle 60 depicted in FIG. 3.The first fuel flow condition 410 provides a fuel-oxidizer ratio,depicted at line 403, at the combustion chamber including the first fuelflow and the second fuel flow.

It should be appreciated that the fuel flow rate A and the fuel flowrate B may generally correspond to one or more of a fuel flow rate ofeach respective fuel flow. However, in other embodiments, the fuel flowrate A and the fuel flow rate B may each correspond to any appropriateparameter indicative of a volume and/or mass rate or other quantity offuel from the fuel system through the fuel nozzle.

It should be appreciated that the fuel-oxidizer ratio 403 generallycorresponds to a total fuel-oxidizer ratio of a total flow of fuel(e.g., a sum of the fuel flow rate A 401 and the fuel flow rate B 402 inFIG. 6, or a sum of the first fuel flow 91 and the second fuel flow 92in FIG. 3) provided to the combustion chamber through the plurality offuel nozzles and the flow of oxidizer provided to the combustion chamberfor mixing and burning with the total flow of fuel. The fuel-oxidizerratio may be calculated based on one or more known methods or otherwisecorrespond to fuel-oxidizer or fuel-air ratios. In certain embodiments,the fuel-oxidizer ratio may correspond to a fuel-air equivalence ratio,an air-fuel equivalence ratio, or other appropriate parametercorresponding to a total quantity, mass, or volume, or flow ratethereof, of liquid and/or gaseous fuel mixed with a total quantity,mass, or volume, or flow rate thereof, of oxidizer and burned ordetonated at the combustion chamber.

The method 1000 includes at 1013 comparing the environmental parametercorresponding to the flow of oxidizer to the first environmentalparameter threshold. If the environmental parameter is equal to orgreater than the first environmental parameter threshold, such as one ormore of the first compressor exit condition parameter or the secondcompressor exit condition parameter depicted at threshold 510 in graph500, the method 1000 may proceed to step 1025 to transition the fuelsystem to a second fuel flow condition, such as depicted at 419 in graph400. In various embodiments, the method 1000 at 1025 occurs whilemaintaining an approximately equal or unchanged fuel-oxidizer ratio atthe combustion chamber during transition from the first fuel flowcondition 410 to the second fuel flow condition 420.

In certain embodiments, the method 1000 includes at 1017 comparing theenvironmental parameter to a second environmental parameter threshold,such as one or more of the first compressor exit condition parameter orthe second compressor exit condition parameter depicted at threshold 520in graph 500, and proceeding to step 1025 if the environmental parameteris less than or equal to the second environmental parameter threshold.

In one embodiment, the method 1000 includes at 1019 comparing a healthparameter to a health parameter threshold. The health parametercorresponds to one or more of a combustor component temperature, acombustion thermal gradient, a combustor stability parameter, or anemissions parameter, such as described in regard to the combustionsection 44 in FIG. 3. In various embodiments, the health parameterthreshold is a predetermined threshold stored in the memory 214 at thecontroller 210. In some embodiments, the health parameter is a functionof time, aircraft altitude, ambient pressure, or other indicator thatmay correspond to a change in emissions requirement or durability of thecombustor component or turbine section. One or more of the time,aircraft altitude, ambient pressure, or other indicator may define anemissions environment at which the cleaning method is allowed to beexecuted. In certain embodiments, the method 1000 at step 1025 occurs ifthe health parameter is within the health parameter threshold.

At 1030, the method 100 includes operating the fuel system at a secondfuel flow condition, such as depicted at 420 on graph 400. The secondfuel flow condition 420 includes a second fuel flow rate A correspondingto the first fuel flow through the first injector of the fuel nozzle.The second fuel flow condition 420 further includes a second fuel flowrate B corresponding to the second fuel flow through the second injectorof the fuel nozzle. The second fuel flow condition 420 provides thefuel-oxidizer ratio at the combustion chamber equal at the first fuelflow condition 410 and the second fuel flow condition 420. Stateddifferently, a total quantity or mass of fuel provided to the combustionchamber at the first fuel flow condition 410 is equal to the totalquantity or mass of fuel provided to the combustion chamber at thesecond fuel flow condition 420. However, as can be appreciated by thedepiction in graph 400, the first fuel flow rate A at the first fuelflow condition 410 differs from second fuel flow rate A at the secondfuel flow condition 420, and the first fuel flow rate B at the firstfuel flow condition 410 differs from the second fuel flow rate B at thesecond fuel flow condition 420.

In a certain embodiment, the second fuel flow condition 420 includes thesecond fuel flow rate A greater than the first fuel flow rate A at thefirst fuel flow condition 410. In still certain embodiments, the secondfuel flow condition 420 includes the second fuel flow rate B less thanthe first fuel flow rate B at the first fuel flow condition 410. In oneembodiment, the method 1000 includes at 1025 transitioning from thefirst fuel flow condition 410 to the second fuel flow condition 420,such as depicted at 419 in graph 400. In various embodiments, the method1000 at 1025 occurs while maintaining an approximately equal orunchanged fuel-oxidizer ratio at the combustion chamber duringtransition from the first fuel flow condition 410 to the second fuelflow condition 420.

In particular embodiments, the second fuel flow rate B is zero at thesecond fuel flow condition 420. In one embodiment, the second fuel flowis shut-off or diverted from flowing through the second injector at thefuel nozzle. In a still particular embodiment, the second fuel flow isshut-off or diverted from flowing through the fuel nozzle generally. Invarious embodiments, the method 1000 includes shutting off or divertingthe second fuel flow from the fuel nozzle and allowing a non-fuel fluidmedium to occupy the second injector of the fuel nozzle. The non-fuelfluid medium may include an oxidizer, such as a portion of the flow ofoxidizer corresponding to the environmental parameter as describedabove, at the second injector. In certain embodiments, operating thefuel system at the second fuel flow condition 420 includes operating thefuel system at a condition at which thermal decomposition of depositsoccurs within the second injector.

In certain embodiments, the second fuel flow condition, such as depictedat 420 in graph 400, corresponds to a cleaning condition at the fuelnozzle. The cleaning condition includes an operating condition at whichfuel is provided through a portion of the fuel nozzle while a cleaningmethod is executed at another portion of the fuel nozzle. In oneembodiment, the cleaning method includes one or more methods forthermally decomposing deposits of fuel within a fuel injector of a fuelnozzle. The method for thermally decomposing deposits of fuel within thefuel injector, such as the second injector 62 depicted in FIG. 3,includes providing fuel to the combustion chamber through another fuelinjector of the fuel nozzle, such as the first injector 61 depicted inFIG. 3. The method further includes transitioning to providing fuelthrough the other fuel injector, such as the second injector 62, andreducing or shutting off fuel through another fuel injector, such as thefirst injector 61.

Various embodiments of the cleaning method include providing a cleaningor purge fluid through the fuel injector while another fuel injector atthe fuel nozzle provides fuel to the combustion chamber. Variousembodiments of the method 1000 include at 1031 flowing a purge fluidthrough the second injector during the second flow condition at step1030. In certain embodiments, flowing the purge fluid removes fuelremaining in the second injector after reducing the second fuel flow tozero. In still various embodiments, the method 1000 includes at 1051flowing a purge fluid through the first injector during the fourth flowcondition at step 1050. Correspondingly, flowing the purge fluid removesfuel remaining in the first injector after reducing the first fuel flowto zero. In still certain embodiments, the purge fluid is one or moreflows of inert gas, oxidizer, or other appropriate fluid egressedthrough the second fuel nozzle. In an exemplary embodiment, the purgefluid is provided from the fuel system 90, such as via the first conduit95 or the second conduit 96. The method 1000 at 1031, 1051 may allow forsubstantially removing liquid fluid from the respective injector, suchas to allow for cleaning, abrasion, thermal decomposition of fuel coke,or another appropriate cleaning process, over a period of time beforere-introducing fuel through the respective injector.

In certain embodiments, the method 1000 includes at 1033 flowing a purgefluid through the second injector during or after the second fuel flowcondition at step 1030. In still certain embodiments, the method 1000includes at 1053 flowing a purge fluid through the first injector duringor after the fourth fuel flow condition at step 1050. In still otherembodiments of the method 1000 at 1033 or 1053, flowing the purge fluidthrough the fuel injector includes a continuous or intermittent flow ofpurge fluid through the respective fuel injector for a period of timeprior to operating the fuel system at the next fuel flow condition. Instill certain embodiments, the method 1000 at 1033 occurs after a periodof time following steps at 1031. In other embodiments, the method 1000at 1053 occurs after a period of time following steps at 1051.

In certain embodiments, the purge fluid is a cleaning fluid or cleaningmedium egressed through the respective fuel injector while the otherfuel injector is providing fuel to the combustion chamber. The cleaningfluid may an inert gas, oxidizer, liquid and/or gaseous fuel, abrasiveparticles, detergents, water-based detergents, or other appropriatecleaning medium, or combinations thereof. In certain embodiments, theabrasive particles include one or more alumina, silica, diamond, nutshells, fruit pit stones, or combinations thereof. In still variousembodiments, the abrasive particles may be any appropriate size suitablefor egress through the fuel injector and the respective opening, such asdepicted in FIG. 3. In particular embodiments, the cleaning medium isany appropriate medium suitable for egress through the fuel injectoralong with fuel deposits or other debris. In some embodiments, thecleaning medium includes particles less than 100 microns in diameter, orless than 80 microns in diameter, 40 microns in diameter, or less than30 microns in diameter, or less than 20 microns in diameter, or greaterthan 10 microns in diameter.

In some embodiments, the purge fluid is the flow of oxidizer includingthe first oxidizer flow condition described herein. In certainembodiments, the fuel nozzle includes one or more features configured toproduce local static pressure differences between portions of the fuelinjector proximate to the combustion chamber and portions distal to thecombustion chamber. Such features may include ramps, openings, divots,depressions, passages, or conduits at the fuel injector, such as at orproximate to a flow path of fuel through the fuel injector.

In other embodiments, the purge fluid is a continuous or intermittentflow of the cleaning fluid, such as to provide a relativelyhigh-pressure purge through the respective fuel injector. In oneembodiment, the purge fluid is a continuous or intermittent flow ofliquid and/or gaseous fuel through the respective fuel injector asincreased or nominal levels of fuel are re-introduced through the fuelinjector to the combustion chamber. In some embodiments, the purge fluidincludes one or more high-pressure pulse purges of the cleaning fluidthrough the fuel injector, such as to remove fuel deposits or otherdebris from the fuel injector.

At 1015, the method 1000 includes determining whether operating thecompressor section at the first oxidizer flow condition at 1010 andoperating the fuel system at one or more of the fuel flow conditionsdescribed in regard to one or more of steps 1020, 1025, 1030, 1035,1040, 1045, 1050, 1055, or 1060, or other steps herein, is within acleaning envelop, such as described herein and depicted at area 505 inFIG. 4. In one embodiment, the cleaning envelop is indicative of theflow of oxidizer being at the first oxidizer flow condition such asdescribed herein, the first fuel flow being at a steady-state conditionfor a predetermined period of time, and further including the healthparameter within the health parameter threshold such as describedherein. In certain embodiments, the health parameter corresponds to oneor more of a compressor section exit temperature of the flow of oxidizer(e.g., T3 _(oxidizer)), a compressor section exit pressure of the flowof oxidizer (e.g., P3 _(oxidizer)), a compressor section exit flow rateof the flow of oxidizer (e.g., W3 _(oxidizer)), a fuel-oxidizer ratio atthe combustion chamber, the first fuel flow condition (e.g., W_(fuelA),P_(fuelA), T_(fuelA), etc., W_(fuelB), P_(fuelB), T_(fuelB), etc.), orcombinations thereof. In certain embodiments, operating the fuel systemat the second fuel flow condition 420 occurs after determining that thefirst oxidizer flow condition and the first fuel flow condition 410 arewithin the cleaning envelop.

In still certain embodiments, the cleaning envelop is indicative of theengine 15 and/or aircraft 100 being in an operational or environmentalcondition or emissions environment allowing for steps of the method 1000to be performed within limits related to certain emissions or noiselimits, such as described herein. In various embodiments, the cleaningenvelop provides a threshold at which the adjusted operation of theengine, such as via the different fuel flow conditions described herein,may be performed while operating within desired emissions and/or noiselimits and/or durability limits of the combustion section or the turbinesection. In certain embodiments, the cleaning envelop may limit theperiod of time at which one or more of the fuel flow conditions isoperated, based on certain emissions and/or noise limits during engineor aircraft operation.

Referring back to FIGS. 5A-5B, in various embodiments, at 1040, themethod 1000 includes operating the fuel system at a third fuel flowcondition, such as depicted at 430 in graph 400, after operating thefuel system at the second fuel flow condition at 1030. The third fuelflow condition 430 includes a third fuel flow rate A of the first fuelflow through the first injector of the fuel nozzle and a third fuel flowrate B of the second fuel flow through the second injector of the fuelnozzle. In various embodiments, the method 1000 includes at 1035transitioning from the second fuel flow condition 420 to the third fuelflow condition 430, such as depicted at 429 in graph 400. In variousembodiments, the method 1000 at 1035 occurs while maintaining anapproximately equal or unchanged fuel-oxidizer ratio at the combustionchamber during transition from the first fuel flow condition 410 to thesecond fuel flow condition 420.

In certain embodiments, the third fuel flow condition 430 issubstantially similar to the first fuel flow condition 410. For example,the third fuel flow condition 430 may include setting or returning thesecond fuel flow through the second injector at an approximately similaror equal condition as the second fuel flow corresponding to the firstfuel flow condition 410. Furthermore, the third fuel flow condition 430may include setting or returning the first fuel flow through the firstinjector at an approximately similar or equal fuel parameter as thefirst fuel flow corresponding to the first fuel flow condition 410.

However, in other embodiments, it should be appreciated that, as fueldeposits, such as fuel coke, should be removed with the increased flowof fuel through the second injector from the second fuel flow condition420 to the third fuel flow condition 430, the third fuel flow condition430 may differ in pressure, flow, or another fuel parameter due toincreased efficiency of the fuel system, the fuel nozzle, the combustionsection, and/or the engine generally. In various embodiments, the firstfuel flow condition 410 includes a first pre-cleaning pressure parameterat the second injector. The third fuel flow condition 430 includes afirst post-cleaning pressure parameter at the second injector. The firstpost-cleaning pressure parameter is less than the pre-cleaning pressureparameter. In certain embodiments, the pre-cleaning pressure parameterand the post-cleaning pressure parameter corresponds to a delta pressure(dP) between an exit of the fuel nozzle (e.g., pressure at thecombustion chamber) versus an upstream fuel pressure, such as at thefuel system. The decreased dP may be indicative of the cleaned fuelinjector. However, in certain embodiments, the method 1000 may includereturning from step 1040 to step 1030, or returning from step 1040 tostep 1020 then step 1030, or returning from step 1040 to step 1020, step1025, step 1030, and then 1035, such as to repeat the cleaning processat the second injector.

In still various embodiments, the first fuel flow condition 410including the pre-cleaning pressure parameter and the third fuel flowcondition 430 including the post-cleaning pressure parameter togetherinclude a substantially equal pre-cleaning flow rate of fuel relative toa post-cleaning flow rate of fuel.

In various embodiments, the method 1000 includes at 1050 operating thefuel system at a fourth fuel flow condition, such as depicted at 440 ingraph 400. The fourth fuel flow condition 440 includes a fourth fuelflow rate A of the first fuel flow through the first injector and afourth fuel flow rate B of the second fuel flow through the secondinjector. The fourth fuel flow rate A is less than the first fuel flowrate A, and the fourth fuel flow rate B is greater than the first fuelflow rate B. The fuel-oxidizer ratio at the combustion chamber isapproximately equal between the first fuel flow condition 410 and thefourth fuel flow condition 440. In various embodiments, thefuel-oxidizer ratio at the combustion chamber is equal between the firstfuel flow condition 410 and the fourth fuel flow condition 440 such asdescribed in regard to the method 1000 at 1020, 1030, or 1040.

In certain embodiments of the method 1000 at 1050, the fourth fuel flowrate A is zero. In still certain instances, the fourth fuel flow rate Bis approximately equal to the total fuel flow at the combustion chambercorresponding to the fuel-oxidizer ratio at the combustion chamber, suchas described in regard to the method 1000 at 1020, 1030, or 1040. In oneembodiment, the method 1000 further includes at 1045 transitioning fromthe third fuel flow condition 430 to the fourth fuel flow condition 440,such as depicted at 439 in graph 400. In various embodiments, the method1000 at 1045 occurs while maintaining an approximately equal orunchanged fuel-oxidizer ratio at the combustion chamber duringtransition from the third fuel flow condition 430 to the fourth fuelflow condition 440. In various embodiments, the method 1000 at 1045 isperformed similarly as described in regard to steps 1025 or 1035.

It should be appreciated that the fourth fuel flow condition 440 andtransitions thereto and therefrom may occur under similar conditions orrequirements at the cleaning envelop described in regard to one or moreof steps 1013, 1015, 1017, or 1019, or other steps described herein.

In still certain embodiments, the method 1000 includes at 1060 operatingthe fuel system at a fifth fuel flow condition, such as depicted at 450in graph 400. The method 1000 may include operating the fuel system atthe fifth fuel flow condition 450 after operating the fuel system at thefourth fuel flow condition 440. The fifth fuel flow condition 450includes a fifth fuel flow rate A of the first fuel flow through thefirst injector and a fifth fuel flow rate B of the second fuel flowthrough the second injector. In certain embodiments, the fifth fuel flowcondition 450 may substantially equal one or more of the first fuel flowcondition 410 or the third fuel flow condition 430.

However, in other embodiments, such as for reasons stated herein inregard to the first fuel flow condition 410 and the third fuel flowcondition 430, it should be appreciated that, as fuel deposits, such asfuel coke, should be removed with the increased flow of fuel through thefirst injector from the fourth fuel flow condition 440 to the fifth fuelflow condition 450, the fifth fuel flow condition 450 may differ inpressure, flow, or another fuel parameter due to increased efficiency ofthe fuel system, the fuel nozzle, the combustion section, and/or theengine generally. In various embodiments, the first fuel flow condition410 includes a second pre-cleaning pressure parameter relative to thefirst injector. The fifth fuel flow condition 450 includes a secondpost-cleaning pressure parameter relative to the first injector. Thesecond post-cleaning pressure parameter at the first injector is lessthan the second pre-cleaning pressure parameter at the first injector.In certain embodiments, the pre-cleaning pressure parameter and thepost-cleaning pressure parameter corresponds to a delta pressure (dP)between an exit of the fuel nozzle (e.g., pressure at the combustionchamber) versus an upstream fuel pressure, such as at the fuel system.The decreased dP may be indicative of the cleaned fuel injector.However, in certain embodiments, the method 1000 may include returningfrom step 1060 to step 1050, or returning from step 1060 to step 1040then step 1050, or returning from step 1060 to step 1040, step 1045,then step 1050, such as to repeat the cleaning process at the firstinjector.

In still particular embodiments, the fifth fuel flow condition 450 maycorrespond to a new or altered nominal fuel flow condition differentfrom another nominal fuel flow condition (e.g., at the first fuel flowcondition 410). For instance, as the fifth fuel flow condition 450follows one or both cleaning steps (e.g., at the second and fourth fuelflow conditions 420, 440), the fifth fuel flow condition 450 maycorrespond to a condition at or after which the engine 15, propulsionsystem 10, or aircraft 100 may proceed with normal operation.

In one embodiment, the method 1000 further includes at 1055transitioning from the fourth fuel flow condition 440 to the fifth fuelflow condition 450, such as depicted at 449 in graph 400. In variousembodiments, the method 1000 at 1055 occurs while maintaining anapproximately equal or unchanged fuel-oxidizer ratio at the combustionchamber during transition from the fourth fuel flow condition 440 to thefifth fuel flow condition 450. In various embodiments, the method 1000at 1055 is performed similarly as described in regard to steps 1025,1035, or 1045.

It should be appreciated that, in various embodiments, the method 1000includes adjusting the fuel flow rate A and the fuel flow rate Bsubstantially simultaneously to maintain an approximately steadyfuel-oxidizer ratio at the combustion chamber when transitioning betweenthe fuel flow conditions such as described herein. It should further beappreciated that simultaneous adjustment or transitioning may includealtering the fuel flow rates at different absolute rates of increase ordecrease, such as to allow for substantially even or steady-statefuel-oxidizer ratio at the combustion chamber.

Various embodiments of the method 1000 described in regard to one ormore of steps 1020, 1025, 1030, 1035, 1040, 1045, or 1050, or othersteps as may be described herein, may include operating the compressorsection to produce and provide the flow of oxidizer defining the firstoxidizer flow condition, such as described in regard to step 1010. In aparticular embodiment, the first oxidizer flow condition corresponds toa steady state inlet condition of oxidizer into the compressor section.The steady state inlet condition of oxidizer into the compressor sectionmay correspond to one or more of a substantially steady or unchangingambient temperature, pressure, density, humidity, or other ambientenvironmental parameter of oxidizer (e.g., ambient air) entering thecompressor section (e.g., at or proximate to the inlet 18, or generallyforward or upstream of the compressor section 42 and/or fan assembly 14depicted in FIG. 2).

In certain embodiments, the substantially steady state condition maygenerally correspond to substantially level flight or unchangingaltitude or attitude. In one embodiment, the steady state inletcondition corresponds to a cruise condition of an aircraft including anengine configured to execute steps of the method 1000. In otherembodiments, the steady state inlet condition may correspond to an idleoperating condition, such as during ground operation of an aircraft orengine, or an in-flight or altitude low-power operation of the engine.In still other embodiments, however, the steady state inlet conditionmay correspond to a part-power operating condition (e.g., climb,descent, approach, etc., or generally less than 100% power) or afull-power operating condition (e.g., takeoff power).

In yet another embodiment, the method 1000 may include at 1005 operatingthe compressor section to produce or provide the flow of oxidizer at aninitial oxidizer flow condition in which the initial oxidizer flowcondition precedes the first oxidizer flow condition. In certainembodiments, the initial oxidizer flow condition corresponds to atransient inlet condition of oxidizer into the compressor section. Forexample, the transient inlet condition of oxidizer may correspond tochanges in ambient oxidizer conditions entering the compressor section.Transient inlet conditions may correspond to changes in temperature,pressure, density, humidity, or other ambient environmental parameter ofoxidizer (e.g., ambient air) entering the compressor section. Transientinlet conditions may correspond to changes in altitude of attitude of anaircraft including an engine configured to execute steps of the method1000.

Referring back to graph 400, certain embodiments of the method 1000include operating the fuel system and the compressor section for periodsof time corresponding to one or more of the modes of operation describedherein. In various embodiments, a period of time may be applied to eachrespective fuel flow condition, such as depicted in regard to 410, 420,430, 440, 450. The period of time may include a predetermined period oftime at one or more of respective steps 1030, 1050, during which thermaldecomposition of fuel or other matter in the respective fuel injectormay form. In still certain embodiments, the period of time is bounded bya time threshold corresponding to a health parameter of one or morecomponents of the combustion section and/or downstream components (e.g.,the turbine section). In various embodiments, the health parameter ofthe one or more components corresponds to a combustor heat shield, acombustor liner, the fuel nozzle, a turbine nozzle, vane, or blade, or adesired life or retention parameter for a thermal barrier coating (TBC)or low-observable coating, or other applicable components at ordownstream of the combustion section.

In particular embodiments, the method 1000 includes at 1015 determiningwhether operating the compressor section at the first oxidizer flowcondition at 1010 and operating the fuel system at one or more of thefuel flow conditions described in regard to steps 1020, 1025, 1030,1035, 1040, 1045, 1050, 1055, or 1060, or other steps herein, is withina cleaning envelop. In one embodiment, the cleaning envelop isindicative of the flow of oxidizer being at the first oxidizer flowcondition such as described herein, the first fuel flow being at asteady-state condition for a predetermined period of time, and furtherincluding the health parameter such as described herein. In certainembodiments, the health parameter corresponds to one or more of acompressor section exit temperature of the flow of oxidizer (e.g., T3_(oxidizer)), a compressor section exit pressure of the flow of oxidizer(e.g., P3 _(oxidizer)), a compressor section exit flow rate of the flowof oxidizer (e.g., W3 _(oxidizer)), fuel-oxidizer ratio at thecombustion chamber, the first fuel flow condition (e.g., W_(fuelA),P_(fuelA), T_(fuelA), etc., W_(fuelB), P_(fuelB), T_(fuelB), etc.), orcombinations thereof. In certain embodiments, operating the fuel systemat the second fuel flow condition 420 occurs after determining that thefirst oxidizer flow condition and the first fuel flow condition 410 arewithin the cleaning envelop.

In still certain embodiments, the cleaning envelop is indicative of theengine 15 and/or aircraft 100 being in an operational or environmentalcondition allowing for steps of the method 1000 to be performed withinlimits related to certain emissions or noise limits, such as describedherein. In various embodiments, the cleaning envelop provides athreshold at which the adjusted operation of the engine, such as via thedifferent fuel flow conditions, may be performed while operating withindesired emissions and/or noise limits. In certain embodiments, thecleaning envelop may limit the period of time at which one or more ofthe fuel flow conditions is operated, based on certain emissions and/ornoise limits during engine or aircraft operation.

Referring back to FIGS. 1-3, the aircraft 100, the engine 15, and/or thefuel system 90 may include a controller 210 configured to execute one ormore steps of embodiments of the method 1000 provided herein. In variousembodiments, the controller 210 can generally correspond to any suitableprocessor-based device, including one or more computing devices. Forinstance, FIG. 2 illustrates one embodiment of suitable components thatcan be included within the controller 210. As shown in FIG. 2, thecontroller 210 can include a processor 212 and associated memory 214configured to perform a variety of computer-implemented functions. Invarious embodiments, the controller 210 may be configured to operate theaircraft 100, the propulsion system 10, the engine 15, and/or the fuelsystem 90 including the fuel nozzle 60, such as shown and describedherein and such as according to one or more steps of the method 1000.

As used herein, the term “processor” refers not only to integratedcircuits referred to in the art as being included in a computer, butalso refers to a controller, microcontroller, a microcomputer, aprogrammable logic controller (PLC), an application specific integratedcircuit (ASIC), a Field Programmable Gate Array (FPGA), and otherprogrammable circuits. Additionally, the memory 214 can generallyinclude memory element(s) including, but not limited to, computerreadable medium (e.g., random access memory (RAM)), computer readablenon-volatile medium (e.g., flash memory), a compact disc-read onlymemory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc(DVD) and/or other suitable memory elements or combinations thereof. Invarious embodiments, the controller 210 may include one or more of afull authority digital engine controller (FADEC), a propeller controlunit (PCU), an engine control unit (ECU), or an electronic enginecontrol (EEC). In still various embodiments, the controller 210 maydefine a distributed network of controllers 210, or a distributednetwork of shared, dedicated, or grouped processors 212 or a network ofmemory 214 storage networked in clusters physically at the aircraft 100,the propulsion system 10, or the engine 15, or physically detached orremote therefrom (e.g., at a ground-based or satellite-based location).

As shown, the controller 210 may include control logic 216 stored inmemory 214. For example, the control logic 216 may define firmwareconfigured to execute instructions for cleaning a fuel nozzle duringoperation of an engine, such as provided in regard to one or more stepsof the method 1000. The control logic 216 may include instructions thatwhen executed by the one or more processors 212 cause the one or moreprocessors 212 to perform operations, such as steps of the method 1000depicted and described herein.

In various embodiments, the controller 210 may include at the memory 214a predetermined table, chart, schedule, function, transfer or feedbackfunction, etc. of fuel flow conditions, rates or rates of change oftransition between fuel flow conditions, fuel parameters, cleaningenvelop, environmental parameters, health parameters, or periods of timeat or over which one or more steps of the method 1000 are executed.

Additionally, as shown in FIG. 2, the controller 210 may also include acommunications interface module 230. In various embodiments, thecommunications interface module 230 can include associated electroniccircuitry (e.g., interface circuitry) that is used to send and receivedata. As such, the communications interface module 230 of the controller210 can be used to receive data from the aircraft 100, the propulsionsystem 10, the engine 15, and/or the fuel system 90, such as, but notlimited to, a compressor section exit temperature of the flow ofoxidizer (e.g., T3 _(oxidizer)), a compressor section exit pressure ofthe flow of oxidizer (e.g., P3 _(oxidizer)), a compressor section exitflow rate of the flow of oxidizer (e.g., W3 _(oxidizer)), afuel-oxidizer ratio at the combustion chamber, the first fuel flowcondition (e.g., W_(fuelA), P_(fuelA), T_(fuelA), etc., W_(fuelB),P_(fuelB), T_(fuelB), etc.), a fuel parameter, cleaning envelop,environmental parameter, health parameters, or timers associated withone or more periods of time described herein, etc. The communicationsinterface module 230 may particularly send and receive data to and fromthe control logic 216 stored in the memory 214.

It should be appreciated that the communications interface module 230can be any combination of suitable wired and/or wireless communicationsinterfaces and, thus, can be communicatively coupled to one or morecomponents of the aircraft 100, propulsion system 10, engine 15 or fuelsystem 90 via a wired and/or wireless connection. As such, thecontroller 210 may operate, modulate, control, adjust, alter, ortransition operation of the aircraft 100, propulsion system 10, engine15, fuel nozzle 60, and/or fuel system 90, such as according to one ormore steps of the method 1000 provided herein.

Various embodiments of the engine 15, fuel system 90, aircraft 100,controller 210, and method 1000 provided herein may provide advantageousimprovements to engine operation by allowing for fuel nozzle cleaningduring engine operation. Improvements include allowing for fuel nozzlecleaning, such as via thermal decomposition or break-down of depositsinto lighter volatile substances that are able to egress the fuelnozzle, without external pressure system, external cleaning systems, orexternal cleaning mediums. Embodiments of the method may be performedregularly during operation of the engine, such as during predeterminedtimes, such as to mitigate carbon or other particulate buildup at a fuelnozzle. Furthermore, or alternatively, improvements include reducing oreliminating maintenance tasks related to removing or replacing fuelnozzles from an engine for cleaning. Still further, embodiments of thesystem and method provided herein may improve life, durability,maintenance, and/or performance of other combustion section and/orturbine section components, such as by reducing or eliminating unevenfuel nozzle spray patterns, reducing circumferential and/or radialthermal gradient variations (e.g., reducing hot spots), or reducingother conditions that may cause uneven or increased wear ordeterioration of certain combustion section or turbine sectioncomponents.

Although depicted in regard to propulsion gas turbine engines, systemsand methods depicted and described herein may be applied generally toturbomachines, gas turbine engines, Brayton cycle machines, or heatengines generally including a fuel nozzle with a first fuel circuit,conduit, or injector separately controllable from a second fuel circuit,conduit, or injector. Furthermore, or alternatively, embodiments ofsystems and methods provided herein may be applied to non-propulsionengines, such as, but not limited to, industrial gas turbine engines,auxiliary power units, marine gas turbine engines, land-based gasturbine engines, etc. In such embodiments, it should be appreciated thatlimits to emissions or noise described herein in regard to an aircraft(e.g., the LTO cycle) may utilize other emissions or noise limits, suchas, but not limited to, limits generally related to greenhouse gases,local ordinances, or other regulations.

However, although embodiments of systems and methods provided herein maybe applied to non-propulsion engines, it should be appreciated thatcertain particular advantages provided herein are allowed for propulsionsystems during operation, or during flight, that may not be allowed orcontemplated by cleaning systems or methods for non-propulsion engines.Furthermore, it should be appreciated that engine operation duringflight, and methods therefor, including changes between transient inletconditions and steady-state inlet conditions such as described herein,provide complexities and potential issues unlike those fornon-propulsion engines or engines for non-aircraft systems.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

Further aspects of the invention are provided by the subject matter ofthe following clauses:

1. A heat engine comprising a compressor section configured to provide aflow of oxidizer to a combustion chamber; a fuel nozzle comprising aplurality of fuel injection openings, wherein the fuel nozzle isconfigured to provide a first fuel flow to the combustion chamberthrough one or more of the fuel injector openings and a second fuel flowto the combustion chamber through one or more of the fuel injectoropenings different from the first fuel flow; a fuel system comprising afirst conduit configured to provide the first fuel flow to thecombustion chamber and a second conduit configured to provide the secondfuel flow to the combustion chamber, wherein the fuel system isconfigured to provide the first fuel flow variably and separate from thesecond fuel flow; and a controller configured to execute operations, theoperations comprising operating the compressor section to provide theflow of oxidizer at a first oxidizer flow condition to the combustionchamber, wherein the first oxidizer flow condition comprises anenvironmental parameter; operating the fuel system at a first fuel flowcondition to produce a fuel-oxidizer ratio at the combustion chamber;comparing the environmental parameter to a first environmental parameterthreshold; and transitioning the fuel system to a second fuel flowcondition corresponding to a cleaning condition at the fuel nozzle ifthe environmental parameter is equal to or greater than the firstenvironmental threshold.

2. The heat engine of any clause herein, wherein the environmentalparameter comprises a temperature parameter and a pressure parameter.

3. The heat engine of any clause herein, wherein the environmentalparameter corresponds to a location at the heat engine downstream of thecompressor section and upstream of the combustion chamber.

4. The heat engine of any clause herein, comparing the environmentalparameter to a second environmental parameter threshold andtransitioning the fuel system to a second fuel flow conditioncorresponding to the cleaning condition at the fuel nozzle if theenvironmental parameter is less than or equal to the secondenvironmental parameter threshold.

5. The heat engine of any clause herein, wherein the first environmentalparameter threshold corresponds to one or more of a temperature of theflow of oxidizer of 550 F or greater or a pressure of 135 psi or greaterdownstream of the compressor section and upstream of the combustionchamber.

6. The heat engine of any clause herein, wherein the secondenvironmental parameter threshold corresponds to one or more of thetemperature of the flow of oxidizer of 1250 F or less or the pressure of315 psi or less downstream of the compressor section and upstream of thecombustion chamber.

7. The heat engine of any clause herein, the operations comprisingcomparing a health parameter to a health parameter threshold, whereinthe health parameter corresponds to one or more of a combustor componenttemperature, a combustion thermal gradient, a combustor stabilityparameter, or an emissions parameter.

8. The heat engine of any clause herein, wherein transitioning the fuelsystem to the second fuel flow condition corresponding to a cleaningcondition occurs if the health parameter is within the health parameterthreshold.

9. The heat engine of any clause herein, wherein the emissions parametercorresponds to an emissions output versus flight mode, wherein theflight mode corresponds to an emissions environment.

10. The heat engine of any clause herein, wherein the cleaning conditioncomprises operating the fuel system at a second fuel flow condition.

11. The heat engine of any clause herein, wherein the cleaning conditioncomprises flowing, through the fuel nozzle, a purge fluid through thefuel nozzle.

12. The heat engine of any clause herein, wherein flowing the purgefluid comprises continuously flowing for a predetermined period of timeof at least a portion of the flow of oxidizer to remove the thermaldecomposition deposit from the fuel nozzle.

13. The heat engine of any clause herein, wherein operating the fuelsystem at the second fuel flow condition comprises reducing the secondfuel flow to zero and increasing the first fuel flow to equal thefuel-oxidizer ratio at the combustion chamber at the first fuel flowcondition.

14. The heat engine of any clause herein, wherein flowing the purgefluid comprises operating the fuel system at a third fuel flow conditionafter operating the fuel system at the second fuel flow condition,wherein the third fuel flow condition and the first oxidizer flowcondition together provide the fuel-oxidizer ratio at the combustionchamber as the first fuel flow condition and the first oxidizer flowcondition.

15. The heat engine of any clause herein, wherein the first fuel flowcondition corresponds to a cruise operating condition.

16. The heat engine of any clause herein, wherein the first oxidizerflow condition corresponds to a steady state inlet condition of oxidizerinto the compressor section.

17. The heat engine of any clause herein, wherein the steady statecondition corresponds to an idle operating condition, a part-poweroperating condition, or a full-power operating condition.

18. The heat engine of any clause herein, the operations comprisingoperating the compressor section to provide the flow of oxidizer at aninitial oxidizer flow condition, wherein the initial oxidizer flowcondition precedes the first oxidizer flow condition.

19. The heat engine of any clause herein, wherein the initial oxidizerflow condition corresponds to a transient inlet condition of the flow ofoxidizer into the compressor section.

20. The heat engine of any clause herein, wherein the plurality of fuelinjection openings comprises a main fuel injector and a pilot fuelinjector.

21. The heat engine of any clause herein, the operations comprisingdetermining whether operating the compressor section at the firstoxidizer flow condition and operating the fuel system at the first fuelflow condition is within a cleaning envelop comprising one or more of acompressor section exit temperature of the flow of oxidizer, acompressor section exit pressure of the flow of oxidizer, a ratio of thetotal fuel flow and flow of oxidizer at the combustion chamber, or thefirst fuel flow condition.

22. The heat engine of any clause herein, wherein operating the fuelsystem at the second fuel flow condition occurs after determining thatthe first oxidizer flow condition and the first fuel flow condition arewithin the cleaning envelop.

23. A controller for a heat engine, the controller configured to executeoperations, the operations comprising operating a compressor section ata steady state inlet condition of oxidizer into the compressor sectionto provide a flow of oxidizer at a first oxidizer flow condition to acombustion chamber; operating a fuel system at a first fuel flowcondition, wherein the first fuel flow condition comprises a first fuelflow rate A of the first fuel flow through a first injector at a fuelnozzle and a first fuel flow rate B of the second fuel flow through asecond injector at the fuel nozzle, and wherein the first fuel flowcondition provides a fuel-oxidizer ratio at the combustion chambercomprising the first fuel flow and the second fuel flow; operating thefuel system at a second fuel flow condition while operating thecompressor section at the first oxidizer flow condition, wherein thesecond fuel flow condition comprises a second fuel flow rate A of thefirst fuel flow through the first injector and a second fuel flow rate Bof the second fuel flow through the second injector, wherein the secondfuel flow condition provides the fuel-oxidizer ratio at the combustionchamber equal between the first fuel flow condition and the second fuelflow condition; and operating the fuel system at a third fuel flowcondition after operating the fuel system at the second fuel flowcondition, wherein the third fuel flow condition comprises a third fuelflow rate A of the first fuel flow through the first injector and athird fuel flow rate B of the second fuel flow through the secondinjector.

24. The controller of any clause herein, the operations comprisingdetermining whether operating the compressor section at the firstoxidizer flow condition and operating the fuel system at the first fuelflow condition is within a cleaning envelop comprising one or more of acompressor section exit temperature of the flow of oxidizer, acompressor section exit pressure of the flow of oxidizer, fuel-oxidizerratio at the combustion chamber, or the first fuel flow condition.

25. The controller of any clause herein, wherein operating the fuelsystem at the second fuel flow condition occurs after determining thatthe first oxidizer flow condition and the first fuel flow condition arewithin the cleaning envelop.

26. The controller of any clause herein, the operations comprisingoperating the fuel system at a fourth fuel flow condition whileoperating the compressor section at the first oxidizer flow condition,wherein the fourth fuel flow condition comprises a fourth fuel flow rateA of the first fuel flow through the first injector and a fourth fuelflow rate B of the second fuel flow through the second injector, whereinthe fourth fuel flow condition provides the fuel-oxidizer ratio to thecombustion chamber, and wherein the fourth fuel flow rate A is less thanthe first fuel flow rate A, and wherein the fourth fuel flow rate B isgreater than the first fuel flow rate B, and wherein the fuel-oxidizerratio at the combustion chamber is approximately equal at the first fuelflow condition and the fourth fuel flow condition.

27. The controller of any clause herein, the operations comprisingadjusting the fuel flow rate A and the fuel flow rate B simultaneouslyto maintain an approximately steady fuel-oxidizer ratio at thecombustion chamber when transitioning between two or more fuel flowconditions.

28. A method for cleaning a fuel nozzle during engine operation, themethod comprising one or more steps of the operations of any clauseherein.

29. A method for cleaning a fuel nozzle during in-flight operation of anaircraft, the method comprising one or more steps of the operations ofany clause herein.

30. An aircraft comprising a propulsion system, the propulsion systemcomprising the heat engine of any clause herein.

31. An aircraft comprising a heat engine, the heat engine comprising thecontroller of any clause herein.

32. An aircraft comprising the controller of any clause herein.

33. A propulsion system comprising the controller of any clause herein.

What is claimed is:
 1. A method for cleaning a fuel nozzle duringoperation of a heat engine including a compressor section, a combustionchamber, and a fuel system, the method comprising: operating thecompressor section to provide a flow of oxidizer at a first oxidizerflow condition to the combustion chamber, wherein the first oxidizerflow condition comprises an environmental parameter; operating the fuelsystem at a first fuel flow condition to produce a fuel-oxidizer ratioat the combustion chamber; comparing the environmental parameter to afirst environmental parameter threshold; and transitioning the fuelsystem to a second fuel flow condition corresponding to a cleaningcondition at the fuel nozzle if the environmental parameter is equal toor greater than the first environmental parameter threshold.
 2. Themethod of claim 1, wherein operating the fuel system at the second fuelflow condition comprises increasing a first fuel flow through the fuelnozzle and reducing a second fuel flow through the fuel nozzle to zeroto equal the fuel-oxidizer ratio at the combustion chamber at the firstfuel flow condition.
 3. The method of claim 1, wherein the first fuelflow condition corresponds to a cruise operating condition.
 4. Themethod of claim 1, wherein the first environmental parameter thresholdcorresponds to one or more of a temperature of the flow of oxidizer of550° F. or greater or a pressure of 135 psi or greater downstream of thecompressor section and upstream of the combustion chamber.
 5. The methodof claim 1, wherein the fuel nozzle comprises a plurality of fuelinjection openings, the method further comprising providing a first fuelflow through the fuel nozzle to the combustion chamber through one ormore of the fuel injection openings, and providing a second fuel flowthrough the fuel nozzle to the combustion chamber through one or more ofthe fuel injection openings different from the first fuel flow.
 6. Themethod of claim 5, wherein the plurality of fuel injection openingscomprises a main fuel injector and a pilot fuel injector.
 7. The methodof claim 1, wherein the environmental parameter comprises a temperatureparameter and a pressure parameter.
 8. The method of claim 7, whereinthe environmental parameter corresponds to a location at the heat enginedownstream of the compressor section and upstream of the combustionchamber.
 9. The method of claim 1, further comprising comparing theenvironmental parameter to a second environmental parameter thresholdand transitioning the fuel system to the second fuel flow conditioncorresponding to the cleaning condition at the fuel nozzle if theenvironmental parameter is less than or equal to the secondenvironmental parameter threshold.
 10. The method of claim 9, whereinthe second environmental parameter threshold corresponds to one or moreof a temperature of the flow of oxidizer of 1250° F. or less or apressure of 315 psi or less downstream of the compressor section andupstream of the combustion chamber.
 11. The method of claim 1, furthercomprising comparing a health parameter to a health parameter threshold,wherein the health parameter corresponds to one or more of a combustorcomponent temperature, a combustion thermal gradient, a combustorstability parameter, or an emissions parameter.
 12. The method of claim11, wherein transitioning the fuel system to the second fuel flowcondition corresponding to the cleaning condition occurs after thehealth parameter is compared to the health parameter threshold.
 13. Themethod of claim 11, wherein the emissions parameter corresponds to anemissions output, which is a function of a flight mode, wherein theflight mode corresponds to an emissions environment at which thecleaning condition can be executed.
 14. The method of claim 1, whereinthe cleaning condition comprises flowing, through the fuel nozzle, apurge fluid through the fuel nozzle.
 15. The method of claim 14, whereinflowing the purge fluid comprises continuously flowing for apredetermined period of time of at least a portion of the flow ofoxidizer to remove fuel deposits from the fuel nozzle.
 16. The method ofclaim 14, wherein flowing the purge fluid comprises operating the fuelsystem at a third fuel flow condition after operating the fuel system atthe second fuel flow condition, wherein the third fuel flow conditionand the first oxidizer flow condition together provide the fuel-oxidizerratio at the combustion chamber as the first fuel flow condition and thefirst oxidizer flow condition.
 17. The method of claim 1, wherein thefirst oxidizer flow condition corresponds to a steady state inletcondition of oxidizer into the compressor section.
 18. The method ofclaim 17, wherein the steady state inlet condition corresponds to anidle operating condition, a part-power operating condition, or afull-power operating condition.
 19. The method of claim 1, furthercomprising operating the compressor section to provide the flow ofoxidizer at an initial oxidizer flow condition, wherein the initialoxidizer flow condition precedes the first oxidizer flow condition. 20.The method of claim 19, wherein the initial oxidizer flow conditioncorresponds to a transient inlet condition of the flow of oxidizer intothe compressor section.